Nanocomposites composed of polymer matrices with nanoparticle reinforcements may be used in the manufacturing of a wide range of products such as automobile components, electronic devices, and food packaging films (see e.g. Giannelis, E. P., Appl. Organometallic Chem., Vol. 12, pp. 675 (1998); and Pinnavaia, T. J., et al, Polymer Clay Nanocomposites, John Wiley & Sons, Chichester, England (2000)). Typically, nanocompsites demonstrate a higher modulus of elasticity and yield strength, as well as enhance electrical/thermal conductivity, than samples manufactured simply from the polymer-based matrix. Clay nanoparticles are often used as a reinforcing agent in the composite. However, depending on the specific application and material characteristics of interest, graphite nanoparticles may be a more attractive choice. Graphite is a very stiff material, with excellent electrical and thermal conductivity. As such, composites manufactured with graphite nanoparticles or “nanoplatelets” may be preferred for many micro-electronic and other applications.
In addition to improved modulus and mechanical strength, graphite nanoplatelets may result in composite materials with a lower percolation threshold relative to electrical conductivity and increased thermal stability. One general problem commonly associated with the incorporation of graphite into composites, however, is the relatively low thermal conductivity in the resultant composite as compared to the graphite itself. Low thermal conductivity may hinder the dissipation of heat from a device or structure made of the composite material. Reduced thermal dissipation, in turn, may cause irreversible damages to the device or structure, or alternatively a complete failure of a composite based system.
Further, while composite materials reinforced with carbon fiber generally have good in-plane properties, the out-of-plane or through-thickness properties tend to be relatively poor by comparison. Research has been conducted to improve through-thickness properties in various composites using nanoparticles of graphite and other materials. This research has included such techniques as the use of carbon nanotubes positioned between carbon fiber plies to improve through-thickness thermal conduction (see e.g. Veedu et al, Nature Publishing Group, 7 May 2006). However, the reported improvements in thermal conductivity are small (˜50%), and the use of expensive nanoparticles cannot be justified.
Hence there is a need for a material and method of manufacturing to address one or more of the drawbacks identified above.